1. Field of the Invention
The invention relates to test equipment for heating and cooling of microelectronic devices to precise temperatures while under electrical test, and specifically to apparatus for rapidly bringing microelectronic devices to selected high or low temperatures.
2. Description of the Prior Art
Microelectronic circuits in production must be tested to determine their characteristics over specified extremes of temperature. For example, such circuits for military applications may require testing at -55.degree. C. and at +125.degree. C. Equipments available in the past for maintaining circuits under test at such temperatures generally fall into two classes: chambers, such as ovens and refrigerators, into which the circuits under test are placed; and jigs or fixtures arranged to hold the circuits with temperature controlled gases or liquids circulated in or around the fixture.
Typical test chambers are disclosed by Frick et al. in U.S. Pat. Nos. 3,408,565 and 3,412,333. The fluid transfer testers are illustrated by U.S. Pat. No. 3,710,251 to Hagge et al. which teaches use of dry nitrogen; and Pat. No. 3,979,671 to Melker et al. describing the use of liquid injection for controlling temperature of a semiconductor chip. Each of such prior art equipments is expensive, large, and inconvenient for rapid testing. To obtain low temperatures, refrigeration equipment has been necessary, which is inherently slow and requires frequent attention and maintenance. Thus, the need clearly exists for a low-cost, easy to use, and fast response device-under-test (D.U.T.) temperature controller.